The invention relates to a capsule for preparing a predetermined quantity of beverage suitable for consumption using an extractable or a soluble product, for instance roast and ground coffee, comprising a circumferential first wall, a second wall closing the circumferential first wall at a first end, a perforate and/or porous third wall closing the circumferential first wall at a second, open, end opposite the second wall arranged for draining the prepared beverage from the capsule, wherein the first, second and third wall enclose an inner space comprising the extractable product.
Such capsules are known per se and can be used in an apparatus for preparing a beverage. They provide convenience in use as well as reproducible extraction conditions, resulting in easy preparation of a cup of coffee with a constant quality. The known capsule can be an open capsule, comprising a circumferential wall and an exit area adapted for draining prepared beverage from the capsule. In the inner space of the capsule, an amount of extractable product, such as roast and ground coffee is provided, for instance by providing an amount of coffee with a smaller volume than the volume of the inner space. Such a capsule can be used in a beverage production apparatus in which a liquid under pressure enters the capsule in order to interact with the extractable product in the capsule and to drain the beverage from the capsule out of the apparatus into a container, such as a coffee cup.
When using the known capsule with an open exit area and loosely provided roast and ground coffee, water supplied to the capsule may rush through the capsule resulting in a less than desired pressure build-up inside the capsule, thereby extracting the coffee with a relatively low extraction pressure. This may result in an uncontrolled beverage preparation process which may adversely affect the prepared beverage. Especially, the quality of the coffee may be inferior, for instance because due to a lower extraction pressure, the coffee may be watery or an inferior foam layer due to a lower CO2 content of the coffee beverage that occurs when extracting at lower extraction pressure, while CO2 is important for creating foam.